A new study suggests that sex-selection may be occurring in Canada, with mothers from certain ethnic communities appearing to be more likely to have boys in their second pregnancies and beyond.

The study, published Monday in the Canadian Medical Association Journal, found that South Korean and East Indian-born women in Canada have an unusually high proportion of boys born as second and third babies.

The researchers are quick to point out they have no way of knowing what accounts for their findings. But the study might be more disturbing evidence that certain ethnic groups may be selectively aborting female fetuses in an effort to have more boys in their families.

The study looked at births in Ontario between 2002 and 2007. The researchers calculated male:female ratio among the births using the mother's country of birth to categorize them.

They found that among women who came to Ontario from South Korea and who were having a second baby, 120 boys were born for every 100 girls.

For mothers who came to Canada from India, there were 111 boys for every 100 girls among second children, and 136 boys for every 100 girls among third children.

Normally in Canada, there are 105 boys born for every 100 girls.

The lead author of the study, Dr. Joel Ray, of St. Michael's Hospital and the University of Toronto, says his team's findings "raise questions."

"Our findings raise the possibility that couples originating from India may be more likely than Canadian-born couples to use prenatal sex determination and terminate a second or subsequent pregnancy if the fetus is female," he and his team write.

The team notes that other studies have made similar findings, but a number of factors make it difficult to draw conclusions.

For example, Ray's and other study teams didn't have access to information on pregnancy terminations among the people in their studies. Nor was there info on whether any previous female babies might have died.

"Knowing that level of detail would help to explain these concerning trends better. In the absence of another plausible explanation, male selection remains the most likely reason for the higher male:female ratios," they write.

But they also point out that if sex selection is occurring, abortion of pregnancies may not be the only method. "It could also be due to sex-selected pre-implantation of male eggs during in vitro fertilization, for example," they write.

The study authors say there needs to be more study on pregnancy termination and IVF practices among families from various world regions.

As well, it would be interesting to know whether other factors affected sex ratios, such as duration of residence in Canada, access to fertility care, family income and parental preferences.

Earlier this year, Dr. Rajendra Kale, who was then the acting editor of the CMAJ, set off a debate with an editorial he wrote suggesting sex selection is being practised by some Canadians of Asian descent.

He suggested that in order to slow the practice, Canadians doctors should adopt policies so that they don't inform women of the sex of their fetus before 30 weeks gestation.